Wastewater-Based Epidemiology of Influenza Viruses: a systematic review

Abstract

Abstract Background Influenza viruses (IVs) are responsible for annual epidemic outbreaks during the winter months. Beyond conventional surveillance systems, the circulation of these pathogens can be monitored using Wastewater-Based Epidemiology (WBE), an epidemiological tool that describes the health status of an entire community by analyzing the presence of pathogens within wastewater. Systematically reviewing existing experiences in this emerging field is crucial to highlight the best practices to establish a WBE surveillance system providing useful information for public health actions. Methods The study protocol for this systematic review has been registered on the PROSPERO website (registration ID: CRD42024532435). Three academic databases (PubMed, Web of Science and Scopus) were accessed to collect studies examining the presence of IVs in wastewater. Studies included were those reporting quantitative measures of viral concentration or detailing molecular/phylogenetic characterization of IVs in wastewater. Results Databases were searched on July 8th, 2024. After de-duplication and screening of the 400 remaining records, 42 were included in the review. IVs detection in wastewater was reported in all papers except from one, although with high variability in terms of positivity titers and concentration levels. More than half of the collected papers (52.4%) evaluated association between environmental viral concentration and clinical data, generally showing concordance between the two aspects. Moreover, 28.6% of papers described subtyping of IVs in wastewater through different methods (specific PCR assays being the most used). Conclusions WBE is a promising approach for surveilling viral circulation, and IVs represent a high value target for implementing this innovative system. Systematically reviewing previous experiences can be useful to obtain information for the establishment of a novel environmental surveillance system of Influenza Viruses Key messages • Nucleic acids belonging to Influenza Virus are detectable in wastewater, even though we report high levels of variability in sampling techniques, laboratory methods and data management systems. • Association between environmental data and number of clinical cases is reported to be generally strong in collected papers; subtyping of IVs present in wastewater is also feasible.